Protein staining compositions and methods

A dye of Formula X:

• ##STR3## or a salt thereof, wherein R.sup.10, R.sup.20, and R.sup.30 are independently selected from the group consisting of hydrogen and alkyl of 1-6 carbon atoms;
• R.sup.40 and R.sup.50 are independently selected from the group consisting of alkyl of 1-6 carbon atoms;
• R.sup.60 is selected from the group consisting of alkyl of 1-20 carbon atoms, phenyl, alkoxyphenyl, wherein the alkyl group is of 1-10 carbon atoms, and alkylphenyl, wherein the alkyl group is of 1-10 carbon atoms;
• and R.sup.70 is a group of Formula XI
• --(C.dbd.O)R.sup.80 XI
• wherein R.sup.80 is selected from the group consisting of alkyl of 1-20 carbon atoms, phenyl, benzyl, phenyl substituted at any one position with alkyl of 1-10 carbon atoms, chloro, bromo, nitro, or cyano, and benzyl substituted at any one position on the phenyl ring with alkyl of 1-10 carbon atoms, chloro, bromo, nitro or cyano.